1. Field of the Invention
The invention relates to a rotary-anode X-ray tube comprising a sleeve bearing with a stationary and a rotatable bearing portion provided with facing bearing faces, at least one of which is provided with a groove pattern, a lubricant which is liquid at least in the operating condition being present between said bearing faces.
2. Description of the Related Art
A rotary-anode X-ray tube of this kind is known from EP-OS 578 314 (U.S. Pat. No. 5,381,456) or from EP-OS 378 274 (U.S. Pat. No. 5,077,775). During rotation of the rotary anode, the lubricant is distributed in the groove pattern in such a manner that a hydrodynamic lubricant film is formed and the two bearing portions "float" on one another. The bearing then operates substantially without wear.
Even though gallium alloys which are generally used as the lubricant in rotary-anode X-ray tubes of this kind have very good lubricating properties, nevertheless wear of the bearing faces may occur, notably when the lubricant is extensively pressed out of the region of the groove pattern after a prolonged period of standstill of the rotary anode or after deceleration of the bearing at high temperatures (or a low lubricant viscosity).